#include <windows.h>
#define ID_TIMER    1 
#define STRMAXLEN  25 //一个显示列的最大长度 
#define STRMINLEN  8  //一个显示列的最小长度
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
////////////////////////////////////////////////////////////////// 
////////////////////////////////////////////////////////////////// 
typedef struct tagCharChain //整个当作屏幕的一个显示列,这是个双向列表 
{
	struct tagCharChain *prev; //链表的前个元素 
	TCHAR  ch;                  //一个显示列中的一个字符 
	struct tagCharChain *next; //链表的后个元素 
}CharChain, *pCharChain;
typedef struct tagCharColumn
{
	CharChain *head, *current, *point;
	int x, y, iStrLen; //显示列的开始显示的x,y坐标,iStrLen是这个列的长度 
	int iStopTimes, iMustStopTimes; //已经停滞的次数和必须停滞的次数,必须停滞的次数是随机的 
}CharColumn, *pCharColumn;
int main(HINSTANCE hInstance, HINSTANCE hPrevInstance,
	PSTR szCmdLine, int iCmdShow)
{
	static TCHAR szAppName[] = TEXT("matrix");
	HWND            hwnd;
	MSG            msg;
	WNDCLASS    wndclass;
	wndclass.style = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc = WndProc;
	wndclass.cbClsExtra = 0;
	wndclass.cbWndExtra = 0;
	wndclass.hInstance = hInstance;
	wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
	wndclass.lpszMenuName = NULL;
	wndclass.lpszClassName = szAppName;
	if (!RegisterClass(&wndclass))
	{
		MessageBox(NULL, TEXT("此程序必须运行在NT下!"), szAppName, MB_ICONERROR);
		return 0;
	}
	hwnd = CreateWindow(szAppName, NULL,
		WS_DLGFRAME | WS_THICKFRAME | WS_POPUP,
		0, 0,
		GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
		NULL, NULL, hInstance,
		NULL);
	ShowWindow(hwnd, SW_SHOWMAXIMIZED); //最大化显示 
	UpdateWindow(hwnd);
	ShowCursor(FALSE); //隐藏鼠标光标 
 
	srand((int)GetCurrentTime()); //初始化随机数发生器 
	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	ShowCursor(TRUE); //显示鼠标光标 
	return msg.wParam;
}
TCHAR randomChar() //随机字符产生函数 
{
	return (TCHAR)(rand() % (126 - 33) + 33); //33到126之间 
}
int init(CharColumn *cc, int cyScreen, int x) //初始化 
{
	int j;
	cc->iStrLen = rand() % (STRMAXLEN - STRMINLEN) + STRMINLEN; //显示列的长度 
	cc->x = x + 3;        //显示列的开始显示的x坐标 
	cc->y = rand() % 3 ? rand() % cyScreen : 0; //显示列的开始显示的y坐标 
	cc->iMustStopTimes = rand() % 6;
	cc->iStopTimes = 0;
	cc->head = cc->current =
		(pCharChain)calloc(cc->iStrLen, sizeof(CharChain)); //生成显示列 
	for (j = 0; j<cc->iStrLen - 1; j++)
	{
		cc->current->prev = cc->point; //cc->point一个显示列的前个元素 
		cc->current->ch = '/0';
		cc->current->next = cc->current + 1; //cc->current+1一个显示列的后个元素 
		cc->point = cc->current++; //cc->point = cc->current; cc->current++; 
	}
	cc->current->prev = cc->point; //最后一个节点 
	cc->current->ch = '/0';
	cc->current->next = cc->head;
	cc->head->prev = cc->current; //头节点的前一个为此链的最后一个元素
	cc->current = cc->point = cc->head; //free掉申请的内存要用current当参数 
	cc->head->ch = randomChar(); // 对链表头的 元素填充 
	return 0;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	HDC          hdc;
	//ctn 用来确定一个显示链是否 向下前进,如果等待次数超过必须等待的次数,ctn就代表要向下前进 
	int i, j, temp, ctn; //j为一个显示链中除链表头外的在屏幕上显示的y坐标,temp绿色过度到黑色之用 
	static  HDC hdcMem;
	HFONT    hFont;
	static  HBITMAP hBitmap;
	static  int cxScreen, cyScreen; //屏幕的宽度 高度. 
	static  int iFontWidth = 10, iFontHeight = 15, iColumnCount; //字体的宽度 高度, 列数 
	static  CharColumn *ccChain;
	switch (message)
	{
	case WM_CREATE:
		cxScreen = GetSystemMetrics(SM_CXSCREEN); //屏幕宽度 
		cyScreen = GetSystemMetrics(SM_CYSCREEN);
		SetTimer(hwnd, ID_TIMER, 10, NULL);
		hdc = GetDC(hwnd);
		hdcMem = CreateCompatibleDC(hdc);
		hBitmap = CreateCompatibleBitmap(hdc, cxScreen, cyScreen);
		SelectObject(hdcMem, hBitmap);
		ReleaseDC(hwnd, hdc);
		//创建字体 
		hFont = CreateFont(iFontHeight, iFontWidth - 5, 0, 0, FW_BOLD, 0, 0, 0,
			DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS,
			DRAFT_QUALITY, FIXED_PITCH | FF_SWISS, TEXT("Fixedsys"));
		SelectObject(hdcMem, hFont);
		DeleteObject(hFont);
		SetBkMode(hdcMem, TRANSPARENT); //设置背景模式为 透明 
		iColumnCount = cxScreen / (iFontWidth * 3 / 2); //屏幕所显示字母雨的列数
		ccChain = (pCharColumn)calloc(iColumnCount, sizeof(CharColumn));
		for (i = 0; i<iColumnCount; i++)
		{
			init(ccChain + i, cyScreen, (iFontWidth * 3 / 2)*i);
		}
		return 0;
	case WM_TIMER:
		hdc = GetDC(hwnd);
		PatBlt(hdcMem, 0, 0, cxScreen, cyScreen, BLACKNESS); //将内存设备映像刷成黑色 
		for (i = 0; i<iColumnCount; i++)
		{
			ctn = (ccChain + i)->iStopTimes++ >(ccChain + i)->iMustStopTimes;
			// 
			(ccChain + i)->point = (ccChain + i)->head; //point用于遍历整个显示列 
 
														//第一个字符显示为 白色 
			SetTextColor(hdcMem, RGB(255, 255, 255));
			TextOut(hdcMem, (ccChain + i)->x, (ccChain + i)->y, &((ccChain + i)->point->ch), 1);
			j = (ccChain + i)->y;
			(ccChain + i)->point = (ccChain + i)->point->next;
			//遍历整个显示列,将这个显示列里的字符从下往上显示 
			temp = 0; //temp绿色过度到黑色之用 
			while ((ccChain + i)->point != (ccChain + i)->head && (ccChain + i)->point->ch)
			{
				SetTextColor(hdcMem, RGB(0, 255 - (255 * (temp++) / (ccChain + i)->iStrLen), 0));
				TextOut(hdcMem, (ccChain + i)->x, j -= iFontHeight, &((ccChain + i)->point->ch), 1);
				(ccChain + i)->point = (ccChain + i)->point->next;
			}
			if (ctn)
				(ccChain + i)->iStopTimes = 0;
			else continue;
			(ccChain + i)->y += iFontHeight; //下次开始显示的y坐标 为当前的y坐标加上 一个字符的高度 
											 //如果开始显示的y坐标减去 整个显示列的长度超过了屏幕的高度 
			if ((ccChain + i)->y - (ccChain + i)->iStrLen*iFontHeight > cyScreen)
			{
				free((ccChain + i)->current);
				init(ccChain + i, cyScreen, (iFontWidth * 3 / 2)*i);
			}
			//链表的头 为此链表的前个元素,因为下次开始显示的时候 就相当与在整个显示列的开头添加个元素,然后在开始往上显示 
			(ccChain + i)->head = (ccChain + i)->head->prev;
			(ccChain + i)->head->ch = randomChar();
		}
 
		BitBlt(hdc, 0, 0, cxScreen, cyScreen, hdcMem, 0, 0, SRCCOPY);
		ReleaseDC(hwnd, hdc);
		return 0;
	case WM_RBUTTONDOWN:
		KillTimer(hwnd, ID_TIMER);
		return 0;
	case WM_RBUTTONUP:
		SetTimer(hwnd, ID_TIMER, 10, NULL);
		return 0;
		//处理善后工作 
	case WM_KEYDOWN:
	case WM_LBUTTONDOWN:
	case WM_DESTROY:
		KillTimer(hwnd, ID_TIMER);
		DeleteObject(hBitmap);
		DeleteDC(hdcMem);
		for (i = 0; i<iColumnCount; i++)
		{
			free((ccChain + i)->current);
		}
		free(ccChain);
		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hwnd, message, wParam, lParam);
}